Embedded vialess bridges

ABSTRACT

Embedded vialess bridges are provided. In an implementation, discrete pieces containing numerous conduction lines or wires in a 3-dimensional bridge piece are embedded where needed in a main substrate to provide dense arrays of signal, power, and electrical ground wires below the surface of the main substrate. Vertical conductive risers to reach the surface plane of the main substrate are also included in the discrete piece, for connecting to dies on the surface of the substrate and thereby interconnecting the dies to each other through the dense array of wires in the discrete piece. The discrete piece to be embedded may have parallel planes of conductors at regular intervals within itself, and thus may present a working surface homogeneously covered with the ends of vertical conductors available to connect surface components to each other and to ground and power at many places along the embedded piece.

RELATED APPLICATIONS

This continuation application claims the benefit of priority to U.S.patent application Ser. No. 15/845,333 to Haba, filed Dec. 18, 2017, nowU.S. Pat. No. 10,083,909 issued Sep. 25, 2018, which in turn claims thebenefit of priority to U.S. patent application Ser. No. 15/354,061 toHaba, filed Nov. 17, 2016, now U.S. Pat. No. 9,852,994 issued Dec. 26,2017, which in turn claims the benefit of priority to U.S. ProvisionalPatent Application No. 62/267,273 to Haba, filed Dec. 14, 2015, all ofthese incorporated by reference herein in their entireties.

BACKGROUND

As microelectronic components become smaller, more wiring and moresignal traces must be miniaturized to fit onto smaller and smallersurface-area footprints of a package substrate. This trend has resultedin very fine conduction lines and high density wiring on the surface ofa conventional substrate. But signal fidelity can suffer when the tracesare very fine. Interference and other degradation can also occur whenthe pitch between lines is very fine for high density interconnects on asurface plane. Besides a signal layer, power and electrical groundconnections may also need to be implemented the same horizontal surfaceof the substrate. When this surface “real estate” of the substratebecomes crowded, there may be a theoretical limit to furtherconcentrating the high conductor count on a given top surface or bottomsurface of the substrate. Conventional miniaturization needed to achievea high density of conductive traces on a given top or bottom surfacearea of the substrate is also expensive.

SUMMARY

This disclosure describes embedded vialess bridges. In animplementation, discrete pieces containing numerous conduction lines orwires in a 3-dimensional bridge piece are embedded where needed in amain substrate to provide dense arrays of signal, power, and electricalground wires below the surface of the main substrate. Verticalconductive risers to reach the surface plane of the main substrate arealso included in the discrete piece, for connecting to dies on thesurface of the substrate and thereby interconnecting the dies to eachother through the dense array of wires in the discrete piece. Thediscrete piece to be embedded may have parallel planes of conductors atregular intervals within itself, and thus may present a working surfacehomogeneously covered with the ends of vertical conductors available toconnect surface components to each other and to ground and power at manyplaces along the embedded piece.

This summary is not intended to identify key or essential features ofthe claimed subject matter, nor is it intended to be used as an aid inlimiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described withreference to the accompanying drawings, wherein like reference numeralsdenote like elements. It should be understood, however, that theaccompanying figures illustrate the various implementations describedherein and are not meant to limit the scope of various technologiesdescribed herein.

FIG. 1 is a diagram of an example vialess bridge piece, including anintegral dense array of conductors for interconnecting microelectronicdevices, embeddable as a second substrate in a main, first substrate.

FIG. 2 is a diagram of the example second substrate and vialess bridgepiece of FIG. 1, embedded in a first substrate to interconnect dies.

FIG. 3 is a diagram of an example signal layer and example power orground layers provided by instances of the example second substrate.

FIG. 4 is a diagram of manufacture stages for embedding the examplesecond substrate, including the integral dense array of conductors, as asignal layer in the first substrate for microelectronic devices.

FIG. 5 is a diagram of manufacture stages for embedding the examplesecond substrate, including the integral dense array of conductors, as apower or ground layer in the first substrate for microelectronicdevices.

FIG. 6 is a flow diagram of an example method of embedding a secondsubstrate in a first substrate for microelectronic devices to provide adense array of wide wires beneath a surface of the first substrate forinterconnecting the microelectronic devices.

DETAILED DESCRIPTION

This disclosure describes example embedded vialess bridges. In animplementation, discrete pieces containing numerous conduction lines orwires in a 3-dimensional bridge piece are embedded where needed in amain substrate to provide dense arrays of signal, power, and electricalground wires below the surface of the main substrate. While theconduction lines in the discrete piece are embedded below the surface ofthe main substrate, vertical conductors or “risers” to reach the surfaceplane of the main substrate are also included in the discrete piece,e.g., for connecting to dies and their pads on the surface of thesubstrate and thereby interconnecting the dies to each other, throughthe dense array of wires in the discrete piece. The discrete piece to beembedded may have parallel planes of conductors at regular intervalswithin itself, and thus may present a working surface homogeneouslycovered with the ends of vertical conductors available to connectsurface components to each other and to ground and power at many placesalong the embedded piece.

Inserting or embedding an example discrete piece, which connects dies toeach other, solves the need for a very high density of interconnectswithout adopting the very fine line aspect required on the horizontaltop surfaces of conventional substrates. The example embedded vialessbridges can provide 3D-ICs, for example, with an ability to placeconnections in a dense array that takes advantage of verticality,without the strict perimeter constraints imposed by conventional finepitch or high density wire-bonded designs.

The dense array of conductors in the example discreet piece (hereinafter“second substrate” or “embedded substrate”) is made integral with thediscrete piece, or second substrate. Since this second substratecontaining the conductors is embedded during formation of the mainsubstrate (“first substrate”), there is no need to create vias, i.e.,individual vertical holes in the main substrate made by drilling, forexample. The creation of conventional vias is thus avoided by theexample system of embedded vialess bridges described herein.

Since the embedded conductors of the embedded substrate can takeadvantage of depth, and are not confined to just the surface plane ofthe main substrate, the individual wires or traces in the embeddedsubstrate piece can be much wider and/or thicker than would be possiblefor the very fine surface traces that conventionally connect dies. Thewider traces in the example second substrate embedded below the surfaceof the main substrate provide more reliable operation, higher signalfidelity, higher current, voltage, and power carrying capacity thanconventional fine traces and wire routing on the surface of conventionalsubstrates. Moreover, the wider traces and wires of the embedded secondsubstrate are less expensive to implement than conventional high densitysurface traces.

The second substrate, or discrete bridge piece, containing conductionlines to be embedded, can be made in many thicknesses, and likewise canbe embedded at different depths, even within the same main substrate.For example, since the second substrate can be embedded at the time ofmanufacture, the second substrate and conduction lines can be createdinside the core of the substrate, or as part of the core itself. On theother hand, in an implementation, a thin version of the second substratecontaining conduction lines can be embedded in an outer layer of thesubstrate, even in an added layer such as an outer dielectric layer orother outer layer of the substrate.

The example embedded second substrate may have numerous verticalconduction risers to reach the surface plane of the main substrate. Thiscan allow surface connection to a given embedded line at multiplesurface points along extent of the line. Depending on construction ofthe embedded second substrate, there may be multiple vertical planes ofvertical risers for signal, power, and electrical ground. In animplementation, this can enable connection to the desired embedded lineat many places on the surface of the main substrate.

As a manufacturing benefit, the second substrate may be embedded withoutundue regard for careful surface tolerances. An example embedment of thesecond substrate may allow a part of the second substrate to protrude or“stick out” from the surface of the main substrate. Since only thevertical risers of the second substrate reach this surface plane of themain substrate, the surface of the substrate may be inexpensively lappedor polished without much regard for how thick of a layer of the embeddedsecond substrate gets subtracted during polish. The vertical risersprovide the same access to their embedded conduction lines regardless ofthe final disposition of the main substrate surface. This is to becontrasted with conventional practice, where lapping can peel, scratchor destroy surface traces. In the example system herein, the onlyconductors of the second substrate accessible at the surface plane ofthe main substrate are vertical risers that can be shortened bypolishing them, without harm.

The second substrate with its integral electrical conductors may beembedded at an angle, such as a 90 degree angle, or other various angleswith respect to the first substrate in order to replace the very fineconventional surface conductors and the fine-pitch routing of suchconventional surface conductors.

The second substrate may be composed of printed-circuit-board (PCB)materials, glass, epoxy, composites, FR-4, plastics, polymers,glass-reinforced epoxy laminate sheets, woven fiberglass cloth withepoxy resin binder, and so forth. In an implementation, planes ofparallel conductors are embedded in the second substrate, during its ownmanufacture.

Instead of very fine and very high density conventional wiring placed ontop of, and parallel to, the surface of the substrate, the embeddedsecond substrate, having planes of conductors rotated 90 degrees withrespect to the surface of the main substrate, contains verticalconductors that take advantage of the depth of the embedment to providedesired wiring and interconnects with wider wires and robust parallelpower and electrical ground plains. These robust vertical conductors canconnect surface components with better conductors in the same or asmaller footprint than conventional layouts, thereby replacingconventional high density surface wiring and conventional finely spacedlines.

Since the embedded conductors can take advantage of the verticaldimension to have multiple planes of horizontal and vertical conductorsbeneath the surface of the main substrate, the embedded second substratecan make finer connections with better conductors and can bridge smallercomponents than conventional fine lines and high density wiring on aconventional substrate surface. Moreover, the example embeddedsubstrates are significantly less expensive than conventional fineconduction lines, while providing higher density wiring connections.

FIG. 1 shows an example second substrate 100 with integral conductors102. In an implementation, the second substrate, to be embedded with itsintegral conductors 102, may be composed of multiple layers, or plates104 made of the selected substrate material, interposed with parallelplanes of conductors 102 integral (and thereby vialess) with thesubstrate material.

In an implementation, an example of the embeddable second substrate 100with integral conductors 102 may be made by arranging conductorsparallel to each other on one or more flat surfaces of a dielectricmaterial, insulation layer, insulator plate, or other suitable substratematerial, stacking or alternating a plurality of such plates, bondingthe plates with the interposed conductors to compile a laminated blockthat has planes of the parallel conductors built-in, and then dicing thelaminated block at 90 degrees to the parallel conductors to form asubstrate with vialess embedded vertical conductors for bridgingcomponents of microelectronic devices. In an implementation, each layerof the example second substrate 100 is a plate 104 with conductivetraces 102 conducting though the plate 104.

FIG. 2 shows an example embedment of embeddable second substrates 100 &100′ in a main substrate 200 of a microelectronics package. In thisexample, the second substrates 100 & 100′ are embedded in a relativelyshallow outer layer 202 of the main substrate 200. A second substrate100 can be embedded much deeper, for example in the core of thesubstrate 200, or as part of the core itself. Vertical conductors 204 ofthe second substrates 100 & 100′ provide electrical contacts or pads onthe top surface of the main substrate 200. The second substrates 100 &100′ provide bridge connections between dies, such as dies 206 & 208,and dies 208 & 210 mounted on the surface of the main substrate 200.Each second substrate 100, or discrete piece, connects dies, such asdies 206 & 208, with each other with high density wiring below thesurface of the main substrate.

FIG. 3 shows embedding of an example second substrate 100 with integralembedded conductors 102 to connect dies 206 & 208 on the surface of themain substrate 200. The embedded second substrate 100 may provide thehigh density conduction lines 102 or wires of a signal layer 302connecting dies, e.g., 206 & 208. The embedded second substrate 100 mayalso be connected with conductors 304 in the main substrate 200, whichin turn are in communication with the opposing side (e.g., bottom) ofthe main substrate 100. A given second substrate 100 may be selectivelyembedded only where needed to make interconnects on the main substrate200.

An embedded second substrate 100′ may also provide a power or anelectrical ground layer 306, or both, to dies 206 & 208 and may connectto power and ground connectors 308 in general on the surface of the mainsubstrate 200. A given embedded second substrate 100 with integralconductors 102 may also provide an electrical bus or high densityelectrical yoke beneath the surface of the main substrate 100. Anembedded second substrate 100 may also replace or constitute part of aredistribution layer (RDL) or fan-in/fan-out area of a microelectronicspackage.

FIG. 4 shows example phases of embedding an example embeddable substrate100 to provide a signal layer within a main substrate 200. A suitablesubstrate material is first selected for the main substrate 200. Adisplacement 402 of the main substrate 200 is designed into manufacture,to embed the embeddable second substrate 100. A surface plane of themain substrate 200 and the embedded second substrate 100 may be polishedor lapped to achieve flatness 404, as described above. Conductive pads406, balls, connectors, etc., may be added by soldering, for example, tothe exposed ends of the vertical conductors 204 of the embedded secondsubstrates 100, for connecting with dies 206 & 208.

FIG. 5 shows example phases of embedding an example embeddable substrate100 to provide a power or electrical ground layer, or both within a mainsubstrate 200. In an implementation, the embeddable second substrate 100is cut or formed, and adhesive may be used in one implementation to bondthe embeddable substrate 100 to the main substrate 200. If the top ofthe embedded substrate 100 protrudes above the surface plane of the mainsubstrate 200, then the entire surface may be lapped or polished forflatness 404. A power bus 504 or line (or a ground bus or line) may beconnected to a conductor 102 of the embedded substrate 100. Conductivepads 406, balls, connectors, etc., may be added by soldering, forexample, to the exposed power or ground bus 504, for connecting withdies 206 & 208.

Example Method

FIG. 6 shows an example method 600 of embedding a second substrate in afirst substrate for microelectronic devices to provide a dense array ofwide wires beneath a surface of the first substrate for interconnectingthe microelectronic devices. In the flow diagram of FIG. 6, operationsof the example method 600 are shown in individual blocks.

At block 602, a second substrate, including a dense array of conductors,is embedded in a first substrate for microelectronic devices.

At block 604, the microelectronic devices are interconnected byattaching the microelectronic devices to vertical conductors of theembedded second substrate, the vertical conductors in communication withthe dense array of conductors in the embedded second substrate.

In the example method 600, the embedded second substrate may compriseelectrical conductors integral with the embedded second substrate toprovide a vialess embedded second substrate.

The example method 600 may further comprise embedding the secondsubstrate inside a core of the first substrate or as part of the core ofthe first substrate during manufacture.

The example method 600 may further comprise embedding the secondsubstrate superficially in an outer layer of the first substrate, ormore deeply in the first substrate, e.g., inside a core of the firstsubstrate or as part of the core of the first substrate.

The embedding may comprise applying an adhesive to bond the embeddedsecond substrate including the dense array of conductors to the firstsubstrate.

Embedding the second substrate in the first substrate may cause thesecond substrate to protrude above the surface plane of the firstsubstrate; and the example method 600 may include lapping or polishingthe second substrate and the first substrate to a flatness of the firstsubstrate, wherein the vertical conductors remain accessible at variabledepths of the lapping or the polishing.

The example method 600 may include integrating numerous wide wires inthe second substrate to comprise the dense array of conductors, andembedding the second substrate in the first substrate to providereplacement of a very fine line aspect of surface traces of the firstsubstrate.

The example method 600 may further comprise integrating numerous widewires at various depths of the second substrate to provide the densearray of conductors.

Conductive pads or balls may be attached to the vertical conductors forconnecting a die to the vertical conductors.

The example method 600 may include embedding the second substrateincluding the dense array of conductors in the first substrate tointerconnect a top surface and a bottom surface of the first substrate.

The example method 600 may also include embedding multiple instances ofthe second substrate at different depths in the same first substrate toprovide signal, power, and ground layers beneath a surface plane of thefirst substrate.

In the specification and appended claims: the terms “connect”,“connection”, “connected”, “in connection with”, and “connecting” areused to mean “in direct connection with” or “in connection with via oneor more elements”; and the term “set” is used to mean “one element” or“more than one element”. Further, the terms “couple”, “coupling”,“coupled”, “coupled together”, and “coupled with” are used to mean“directly coupled together” or “coupled together via one or moreelements”. As used herein, the terms “up” and “down”, “upper” and“lower”, “upwardly” and downwardly“, “upstream” and “downstream”;“above” and “below”; and other like terms indicating relative positionsabove or below a given point or element are used in this description tomore clearly describe some embodiments of the disclosure.

While the present disclosure has been disclosed with respect to alimited number of embodiments, those skilled in the art, having thebenefit of this disclosure, will appreciate numerous modifications andvariations there from. It is intended that the appended claims coversuch modifications and variations as fall within the true spirit andscope of the disclosure.

1. A vialess bridge, comprising: a bridge substrate of a nonconductivematerial bearing electrical conductors, the bridge substrate capable ofbeing embedded in a surface layer or a surface coating of a mainsubstrate; the electrical conductors comprising an array of signal,power, and ground wires; and parallel vertical layers in the substrate,each parallel vertical layer made of individual electrical conduits,each layer of conduits interleaved with a layer of the nonconductivematerial to form a laminate block providing conductors for coupling afirst die to a second die.
 2. The vialess bridge of claim 1, wherein theconductors for coupling a first die to a second die comprise horizontalconduits connecting first vertical conductors to second verticalconductors to enable surface-to-surface electrical connections on themain substrate using the array of the vialess bridge.
 3. The vialessbridge of claim 1, further comprising a working surface containingsurface portions of the vertical conductors.
 4. The vialess bridge ofclaim 3, wherein signal, power, and ground connections are available atmultiple locations and at regular intervals over the working surface. 5.The vialess bridge of claim 1, wherein the bridge substrate isapplicable to a surface of the main substrate to provide the dense arrayof signal, power, and ground wires for interconnecting multiple dies onthe surface of the main substrate.
 6. The vialess bridge of claim 2,further comprising a working surface containing surface portions of thevertical conductors and wherein the horizontal conduits have a depthdimension relative to the working surface that is greater than a widthdimension of the horizontal conduits relative to the working surface. 7.The vialess bridge of claim 2, further comprising a working surfacecontaining surface portions of the vertical conductors, wherein at leastsome of the vertical conductors extend from the working surface toanother surface of the bridge substrate opposite the working surface. 8.An assembly, comprising: a first substrate with conductive traces at afirst line aspect; a second substrate embedded in the first substratewith conductive traces at a second line aspect finer than the first lineaspect, the second line aspect of the second substrate providing adenser array of conductive lines than the first substrate; and parallelvertical layers in the second substrate, each parallel vertical layermade of individual electrical conduits, each layer of conduitsinterleaved with a layer of the nonconductive material to form alaminate block providing vialess vertical conductors.
 9. The assembly ofclaim 8, further comprising horizontal conduits between at least some ofthe vialess vertical conductors to enable point-to-point electricalconnections on the first substrate of the circuit board using the denserarray of the second substrate.
 10. The assembly of claim 9, wherein thedense array of the second substrate bridge provides a socket for a 3D-ICdie or package.
 11. The circuit board of claim 9, wherein the densearray of the second substrate provides interconnects for a 3D-IC die orpackage.
 12. The assembly of claim 9, wherein the dense array of thesecond substrate provides interconnects between multiple 3D-IC dies orpackages.
 13. The assembly of claim 8, further comprising a workingsurface on the second substrate homogenously covered with ends of thevialess vertical conductors.
 14. The assembly of claim 13, wherein theworking surface provides signal, power, or ground connections atmultiple locations and at regular intervals over the surface area of theworking surface.
 15. The assembly of claim 8, wherein the secondsubstrate is applicable to a surface of the first substrate of thecircuit board to provide the dense array of signal, power, and groundwires for interconnecting multiple dies on the surface of the circuitboard.
 16. The assembly of claim 8, further comprising multipleinstances of the second substrate embedded in the first substrate, toprovide multiple areas of the dense array of conductive lines on thesurface of the circuit board.
 17. The assembly of claim 9, wherein thesecond substrate provides at least one signal conduction layer in one ormore additional planes parallel to the plane of the surface, the atleast one signal conduction layer comprising conductors at one or morevertical depths from the surface, a horizontal pitch of the conductorsat the one or more vertical depths determined by thicknesses of thelayers of nonconductive insulator material of the parallel verticallayers.
 18. The assembly of claim 17, wherein the at least one signalconduction layer comprises wide conduction traces or wires in at leastone vertical plane of the parallel vertical layers providing a highersignal fidelity, a higher current-carrying capacity, a higher voltagecapacity, or a higher power-carrying capacity than traces or wirerouting on the surface of the first substrate of the circuit board. 19.The assembly of claim 8, wherein the second substrate provides at leastone power plane in a vertical plane or at least one ground plane in avertical plane accessible to microelectronic devices on the surface ofthe circuit board.
 20. The assembly of claim 8, wherein the secondsubstrate provides a vialess vertical conductor from a first surface ofthe assembly to an opposing surface of the second substrate.